i have had only one dream in which i found a snake in it.
the dream starts out with me wandering around in a building. the building is sort of like an MC Escher drawing.
In the dream, i basically call BS on it, i was looking for an exit, but there was none.
immediately after calling bs on the dream, i am now sitting at a table, with some other people, who are complaining to me that their refrigerator is possessed.*
I get up from the table, open the door, pull out the bottom drawer (this is all done instinctively so to speak) and in the bottom drawer is some water.
in the water is a manifestation of a serpent. meaning, the serpent had no physical form, the water was taking the form of a serpent, slashing about in the water.
i say to the serpent "i command you to die in the name of Jesus Christ" and at that moment the manifestation of the water in the form of a snake turns into something like a tree root, but dead.
I pick up the dead tree root, open a window, and dump it. the dream ended at that instant.
anyhow. i hope you found that amusing, honestly its one of the more hilarious dreams i've ever had. but you need to ponder why you didn't call upon God in the dream. that is not to accuse you, but rather plant the seed that you can deal with a dream, while you're in the dream. no need to pray about it after you wake up.
as for the theology that dream presented, of course its not real. the demons are already dead, cannot be killed again.
*i have had to deal with real people in real life who insist their house, car, (no, not refrigerator, but nothing would supprise me) is possessed. i have had enough weird stuff happen i know better than to tell them they are possessed. so instead, you have to sit and reason with them, ask them in great detail exactly what they experienced, ask the difficult questions, etc.